Systems for recommending various recommended objects to others through Web sites are known. For example, Patent Literature 1 describes a sales promotion system for facilitating sales promotion of products by introduction. In this sales promotion system, an introducer who has purchased products using a mobile terminal selects a product desired to be recommended to others from the products for which the payment is done, and a recommendation advertising ID of the selected product is provided to a person to whom introduction is made. Further, Patent Literature 2 describes a membership management system that introduces others to become a member using a mobile terminal. In this membership management system, when a first mobile terminal notifies the email address of a second mobile terminal to a server, the server notifies the URL of an application to be downloaded when becoming a member to the second terminal by email.